Mate in 5 Exercise 12

White plays and wins in 4 moves https://lichess.org/23CqnHih

1. Kc6 Ka8 2. Kc7 Ka7 3. Nc8+ Ka8 4. Bc6#

The analysis board does checkmate in 5 moves

1. Kc6 Kb8 2. Kb6 Ka8 3. Kc7 Ka7 4. Nc8+ Ka8 5. Bc6#

Source:

https://www.amazon.com/Chess-Puzzles-Advanced-Expert-Level/dp/B0917YQZP1